The present invention relates generally to systems in which it would be desirable to detect events or sequences of events and, in an embodiment described herein, more particularly provides a boiler system ignition sequence detector.
In many electromechanical systems, or simply electrical or mechanical systems, an event or sequence of events should occur in the normal course of operation. However, if the event or sequence of events do not occur as desired, remedial or emergency operations may need to be performed to restore the system to normal operation. Thus, a detector which is able to indicate when an event or sequence of events does not occur as desired would be very useful in these circumstances.
In the case of a boiler system, a desired sequence of events may be as follows: fuel is supplied to the boiler system, electrical power is supplied to the boiler system, a pilot valve is opened, a flame is ignited at a pilot burner, a thermostat indicates a need for heat, a main valve is opened, a flame is ignited at a main burner, the thermostat indicates that additional heat is not needed, the main valve is closed, etc. Several of these events are typically controlled by an ignition control module of the boiler system. For example, the ignition control module may control when the pilot valve opens, ignition of the pilot flame, opening of the main valve, etc.
Hazardous conditions may result if an improper sequence of events occurs in a boiler system. For example, if the main valve is opened before the pilot valve is opened, fuel may accumulate within the boiler system and lead to uncontrolled burning or explosion. As another example, if the main valve is opened before the thermostat indicates a need for heat, the boiler may become overheated.
In the past, simple relays have been used to ensure that a proper sequence of events has occurred in a boiler system. In this manner, for example, power could not be supplied to a main solenoid valve unless power had been previously supplied to a pilot solenoid valve and the thermostat had previously indicated a need for additional heat. Unfortunately, such types of relay networks are easily fooled and may fail to react if a sequence of events, although improper, does not occur exactly as prescribed. Additionally, such event detectors usually were constructed with relatively large and expensive mechanical latching relays. Due to the high radio frequency transmissions produced by ignition of the pilot flame, construction of a generally solid state event detector was thought to be unfeasible.
From the foregoing, it can be seen that it would be quite desirable to provide an event detector for electrical, mechanical, electromechanical or electronic systems which is capable of accurately detecting the occurrence of an event or sequence of events in the system, and which is suitable for use in high RFI level environments. When used in a boiler system, it would be desirable for the event detector to further be able to shut down the boiler system if an improper event or sequence of events occurs, and for the event detector to maintain the boiler system in this state until it is manually reset. It is accordingly an object of the present invention to provide such an event detector and associated methods of protecting systems.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a latching event detector is provided which uses solid state technology, utilization of which does not require a network of mechanical relays, but which is usable in high RFI environments. Methods of protecting systems are also provided.
In broad terms, a latching event detector is provided which includes at least one event detector, each of which is interconnected to a corresponding element of a system, so that each detector is capable of indicating when an event has occurred for its corresponding element. The output of each event detector is interconnected to a microprocessor. The microprocessor is programmed and interconnected to the system, such that the system is disabled when an improper event or sequence of events occurs. The system can be subsequently enabled by manually resetting the latching event detector while primary power is applied thereto.
In the disclosed and described embodiment, the event detectors are interconnected to a pilot valve, a main valve and a thermostat of a boiler system. When an improper sequence of events occurs, an ignition control module of the boiler system is disabled by removing primary power therefrom, thereby removing power from the pilot and main valves. Primary power may be restored to the ignition control module by depressing a reset switch of the latching event detector while power is supplied thereto.
A method of protecting boiler systems is also provided, which method includes the steps of reading the recorded state of a relay and determining whether a fault has occurred by reading the outputs of one or more event detectors. If a fault is detected, the relay is unlatched and the unlatched state is recorded in an EEPROM. Upon subsequent power-up, if an unlatched state is recorded in the EEPROM, the relay may be latched only if a reset switch is closed.